XPath(XML Path language)是一種處理XML文檔段的語言。XSLT(Extensible Stylesheet Language Transformations,可擴展樣式表語言轉換)使用XPath描述表達式和地址路徑控制節點選取。XSLT可以將XML轉換為各種格式，如Html或其他格式。
下面用一個郵件合並程序來簡要說明XPath的串函數。下面的XML文件中包含數據，XSLT文件中包含對郵件格式的定義。MSXML4.0對XML文檔應用樣式表，產生一個合並的郵件文本文檔。
XML文件 Letter.XML
<?XML version="1.0" encoding="UTF-8"?>
<Letter>
<Date>July 17, 2002</Date>
<To>
<FirstName>Vicky</FirstName>
<LastName>P</LastName>
<Sex>Male</Sex>
</To>
<Address>
<Line1>900 National Pkwy</Line1>
<Line2>Suite 105</Line2>
<City>Bellevue</City>
<State>WA</State>
<Zip>98007</Zip>
<Country>USA</Country>
</Address>
<Subject>ESTATE OF JOHN DOE / FILE NO. 12345.6789</Subject>
<Text>
Please pay the property taxes as soon as possible.
</Text>
<Sender>
<FirstName>John</FirstName>
<LastName>M</LastName>
<Title>Sr. Tax Consultant</Title>
</Sender>
</Letter>
XSLT樣式表文檔 Letter.xsl
<?XML version='1.0' encoding="utf-8"?>
<xsl:stylesheet version="1.0"
XMLns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" indent="yes"/>
<xsl:variable name="NL" select="'
'" />
<xsl:variable name="Para" select="concat($NL, $NL)" />
<xsl:template match="/">
<xsl:value-of select="//Date" />
<xsl:value-of select="$Para" />
To,
<xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" />
<xsl:value-of select="$NL" />
<xsl:value-of select="//Address/Line1" />
<xsl:value-of select="$NL" />
<xsl:value-of select="//Address/Line2" />
<xsl:value-of select="$NL" />
<xsl:value-of select="concat(//Address/City, ' ', //Address/State, ' ', //Address/Zip)" />
<xsl:value-of select="$NL" />
<xsl:value-of select="//Address/Country" />
<xsl:value-of select="$Para" />
Regarding: <xsl:value-of select="//Subject" />
<xsl:value-of select="$NL" />
Dear <xsl:if test="starts-with(//Sex, 'M')">Mr. </xsl:if><xsl:if test="starts-with(//Sex, 'F')">Miss </xsl:if>
<xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" />,
<xsl:value-of select="$Para" />
<xsl:value-of select="//Text" />
<xsl:value-of select="$Para" />
Sincerely,
<xsl:value-of select="$Para" />
<xsl:value-of select="concat(//Sender/FirstName, ' ', //Sender/LastName)" />
<xsl:value-of select="$NL" />
<xsl:value-of select="//Sender/Title" />
</xsl:template>
</xsl:stylesheet>
上面的樣式表舉例說明了concat和starts-with XPath串函數和怎樣在輸出文本中增加新行，還有定義和使用變量。
下面是程序的執行結果。
1.VC6建立Win32控制台應用程序。
2.在stdafx.h中添加下面的代碼：
#include <TCHAR.H>
#include <stdio.h>
#include <time.h>
#import "msXML4.dll"
// If this import statement fails, you need to install MSXML 4.0 SP1 from:
//http://msdn.microsoft.com/downloads/sample.ASP?url=/MSDN-FILES/027/001/766/msdncompositedoc.XML
#include <msXML2.h>
// If this include statement fails, you need to install MSXML 4.0 SP1 SDK from:
//http://msdn.microsoft.com/downloads/sample.ASP?url=/MSDN-FILES/027/001/766/msdncompositedoc.XML
// You also need to add the include file and library search path
// to Visual C++'s list of directories (Tools > Options... > DirectorIEs).
using namespace MSXML2;
inline void EVAL_HR( HRESULT _hr )
{ if FAILED(_hr) throw(_hr); }
#define TEMP_SIZE _MAX_PATH // size of short buffer
static _TCHAR szTemp[TEMP_SIZE]; // multipurpose buffer on stack
static DWord dwLen;
3.上面的代碼引入MSXML4類型庫，包含MSXML頭文件，檢查HRESULT值並聲明了一些全局變量。
4.main函數：
int main(int argc, char* argv[])
{
try
{
EVAL_HR(CoInitialize(NULL));
// Make sure that MSXML 4.0 is installed
if (!isMSXMLInstalled())
return -1;
// Make sure that XML and XSL file names are passed
// as command line parameters
if (argc < 3)
// Show proper message here
return -1;
IXMLDOMDocument2Ptr pXMLDoc = NULL;
IXMLDOMDocument2Ptr pXSLDoc = NULL;
// Load the XML document
if (loadDocument(pXMLDoc, argv[1], true))
{
// Load the stylesheet
if (loadDocument(pXSLDoc, argv[2], false))
{
_FTPrintf(stdout, pXMLDoc->transformNode(pXSLDoc));
}
else
{
printMSXMLError(pXSLDoc);
}
}
else
{
printMSXMLError(pXMLDoc);
}
}
catch(...)
{//exception handling
}
_FTPrintf(stdout, "\n\nPress Enter to continue...");
getchar();
CoUninitialize();
return 0;
}
5.XML文件和XSLT樣式表文件名作為命令行參數傳遞給應用程序。主函數通過調用isMSXMLInstalled驗證 MSXML4.0是否安裝。接下來兩次調用loadDocument;先是加載XML文檔,然後是加載XSLT樣式表。 最後調用transformNode進行轉換。
6.本例代碼下載：http://www.perfectxml.com/CPPMSXML/downloads/20020716MailMerge.zip
譯自PerfectXML